#include <bits/stdc++.h>
using namespace std;
using uint=unsigned int;
using ll=long long;
using ull=unsigned long long;
using i128=__int128;
const int N=5e3+5;

double g[N];
double f[N];
int n,x;
double p[N],ans;

void solve(){
    cin>>n>>x;
    for(int i=1;i<=n;i++){
        cin>>p[i];
        p[i]/=100;
    }
    memset(g, 0, sizeof(g));
    g[0]=1;
    for(int i=1;i<=n;i++){
        for(int j=n;j>=1;j--){
            g[j]=g[j]*(1-p[i])+g[j-1]*p[i];
        }
        g[0]*=(1-p[i]);
    }
    f[0] = 0;
    for(int i=1;i<=x;i++){
        double sum = 0;
        for(int j=1;j<=n;j++){
            sum += f[max(0,i-j)] * g[j];
        }
        f[i] = (1 + sum) / (1 - g[0]);
    }
    
    printf("%.8lf",f[x]);
    return;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    solve();
    return 0;
}